Need to put probabilty on quiz

Question

There's a quiz question that I got wrong because there is no indication whether the speaker sees the event as probable or not.  A note on this would help so we don't have to guess.

Accepted Answer

Hola Marcos
You got this one incorrect:
Escribe la dirección del hotel, por si ___. 
(se te olvida / se te olvide)
The only possibility here is the indicative "se te olvida" even without mentioning what grade of probability, as the present subjunctive is never an option with por si/por si acaso. There is a short important note by the end of the lesson (I imagine you missed it when reading through the lesson)
I hope it clarifies it.
Saludos

Answer

Aha, I wasn’t seeing the distiction between the use of the imperfect subjunctive and that of not using the present subjunctive.  For some reason I was just thinking of the subjunctive mood in a generic way.  Thanks for helping me resolve this issue.